1. Field of Invention
The present invention relates to a photovoltaic module and, more particularly, to a solar tracker for a photovoltaic module.
2. Related Prior Art
A photovoltaic module includes a solar cell array mounted on a frame and a solar tracker for directing the solar cell array to the sun. Thus, the photoelectric efficiency of the solar cell array can be maximized.
A typical solar tracker includes the follow properties. Firstly, it tracks the brightest object in the sky. Secondly, it includes detectors for detecting the position of the brightest object. Thirdly, its tolerance is 1 to 3 degrees. Fourthly, it includes an analog circuit.
Referring to FIG. 5, as devised by Ronald P. Corio et al., a conventional solar tracker includes a shell 31, a circuit board 32 located in the shell 31 and four photo detectors 33 provided on the shell 31. The shell 31 includes four walls. Each of the photo detectors 33 is located on a related one of the walls of the shell 31. The photo detectors 33 are located at 45 degrees upward. The photo detectors 33 are directed to the east, the west, the south and the north, respectively. Each of the photo detectors 33 detects the brightness of the sunlight and provides a signal corresponding to the brightness. The intensities of the signals from the photo detectors 33 are calculated to determine the position of the sun.
Problems have however been encountered in the use of the conventional solar tracker. Firstly, the tolerance is larger than 0.5 degrees. Among the photovoltaic modules, concentration photovoltaic modules are the most promising ones for high efficiencies. Among the concentration photovoltaic modules, those including III-V solar cells are the most popular ones. For a concentration photovoltaic module, the tolerance must be smaller than 0.1 degrees.
Secondly, the circuit board 32 consumes much energy because it carries an analog circuit.
Thirdly, it is difficult and therefore expensive to provide the photo detectors 33 on the walls of the shells at 45 degrees upwards.
Fourthly, it is not reliable because it could easily be contaminated by water and dirt.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.